The Linux/GNU CAD CAM project is large there is no doubt about that. It is my firm belief that the project is on the correct track and that by spending time up front drawing block diagrams, brainstorming, writing prototype code, which maay very well be tossed on the recycle heap, is the best way to proceed.
Once there is a final draft of the design document project members will need to review it and determine if what has been designed will meet their needs and the needs of machine shop owner and/or operators.
While it is hard to resist the temptation to jump right in there and start coding, it is necessary to resist that temptation. Once the final draft is finished there will be plenty of time to write code.
Feedback is definitely needed to flesh out several more levels of detailed block diagrams. When project members and potential users agree upon the final draft of the block diagram design documents, further detailed information can be written to add further guidance to the project developers.